Evaporation rate, tear LLT, ocular comfort, tear stability, and production were adversely affected by low RH. The tear film parameters observed after exposure to a desiccating environment for 1 hour were similar to those of the dry eye patient. Therefore, to avoid tear film disruption and possible ocular surface damage, the environmental conditions of dry locations need to be improved or the tear film should be protected against adverse environmental conditions.

Ambient temperature has a considerable effect on human tear film characteristics. Tear evaporation rate, tear LLT, tear stability, and OST were considerably affected by ambient temperature. Chronic exposure to low ambient temperature would likely result in symptoms of dry eye and ultimately ocular surface disorders.

BackgroundReading from tablets is fundamental to modern culture. This study measured differences in the blink rate and symptoms of ocular discomfort in healthy participants during reading from a tablet and a paper book.MethodsForty healthy, normal males subjects were recruited for this study. Subjects were video recorded during reading a text presented on an electronic device (9.7 inch tablet) and a hard copy format, for 15 min. Ocular discomfort experienced during reading was scored using a visual analog scale. Each participant was examined performing one of the two tasks (randomized) on one visit and the other on a separate visit (crossover design). All subjects were evaluated before the reading tasks and every 5 min during 15 min of reading.ResultsThe mean ± standard deviation blink rate was 19.74 ± 9.12/min at baseline. The blink rate decreased significantly under both reading conditions (to 11.35 ± 10.20 and 14.93 ± 10.90/min when reading from a book and a tablet, respectively). There was no significant difference in the blink rate over 15 min during either type of reading. The mean discomfort symptom scores were 148 for the book and 134 for the tablet; both were significantly higher than baseline. A gradual increase in symptoms was found every 5 min during both types of reading.ConclusionThe study confirmed that both the blink rate and ocular discomfort symptoms were strongly affected during performance of close visual tasks. Both reading conditions affected blinking; this may interfere with tear film dynamics. Such effects were reflected in the immediate development of ocular symptoms, which increased significantly during both types of reading.

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